Refractory coated and dielectric coated flame resistant insulating fabric composition

ABSTRACT

Fabric base compositions having a refractory coating on one side and a coating containing finely divided dielectric on the other side exhibit superior flame and heat resistance and superior dielectric properties.

CROSS REFERENCES TO RELATED APPLICATIONS

This is a continuation-in-part of commonly assigned U.S. patentapplication Ser. No. 294,771, filed Aug. 20, 1981, now U.S. Pat. No.4,358,500 and is related to commonly assigned U.S. patent applicationSer. No. 294,770, filed Aug. 20, 1981; Ser. No. 225,888, filed Jan. 19,1981; Ser. No. 073,362, filed Sept. 7, 1979, now U.S. Pat. No.4,282,284; Ser. No. 931,121, filed Aug. 4, 1978, now abandoned, andthree concurrently filed patent applications, the first relating to arefractory coated fabric composition prepared by plasma spraying, thesecond relating to a refractory coated/vapor barrier coated fabriccomposition and the third relating to a refractory coated/conductivelayer coated fabric composition.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to heat and flame resistant, flexible, insulatingfabric compositions. More particularly, it relates to refractory coatedand dielectric coated base fabric compositions. This inventionespecially relates to refractory coated and dielectric coated basefabric compositions wherein the refractory coating is formed on one sideof the fabric and the dielectric coating is formed on the other side.

2. Description of the Prior Art

Asbestos and other thermal protection materials are employed asprotective mats for welding operations, furnace linings, fire-resistantlinings and the like to provide protection from flames and thermalextremes as well as for dissipation of heat at a high rate. Although ineach application reasonable performance is obtained, the selectedmaterial has limitations in its range of uses and in its effectiveness,even in uses for which it is particularly adapted. In addition, asbestoshas found less utility in certain uses because of recent findings thatit may constitute a health hazard.

Ceramics and/or glass fibers have been used heretofore to prepare hightemperature electrical insulating tape. In addition, coated fabrics andceramic structures have been prepared with a combination of glass fiberfabrics and metal oxides.

U.S. Pat. No. 4,282,284 and commonly assigned patent applications Ser.Nos. 225,888 and 294,770 disclose a heat resistant, flexible,refractory, insulating fabric composition of a porous base fabric,preferably a knitted fiberglass fabric, coated with heat resistantrefractory materials, such as alumina and zirconia, and an organicbonding agent, such as acrylic latex alone or admixed with colloidalsilica. A polymeric coating, such as polyvinyl chloride, may be formedover the coated fabric to provide abrasion resistance to thecomposition. A feature of this composition resides in the fact that therefractory materials are bonded in the interstices as well as to thesurface of the base fabric, such that a significant amount of thefabric's flexibility and stretch properties are retained. This fabriccomposition has a variety of uses and therefore may be employed as thedielectric in insulated electrical wire or cable, as protective mats andcurtains in welding operations, as linings for fire resistant machineand appliance covers, as duct and pipe insulation, as wrappings forengine exhaust systems and the like. When this fabric composition isexposed to heat and high temperatures, the organic bonding agentcontaining the refractory materials will decompose, causing therefractory materials to fuse into the softened surface of the knitfiberglass base fabric, enabling it to withstand intense heat andelevated temperatures well beyond the normal melt temperature of thefiberglass fabric. The resulting fabric structure will have ceramicqualities and will not soften, melt, drip or lose its insulatingproperties.

Although the organic components of the bonding agent of these prior artfabric compositions may not produce a flame when exposed to a flame orthe intense heat developed by a flame, i.e. temperature of 1750° F. andabove, they will decompose at these temperatures resulting in someproducts of combustion in the form of smoke and fumes which may proveharmful to persons in the vicinity.

Commonly assigned patent application Ser. No. 294,771 discloses improvedrefractory coated fabric compositions which eliminate the products ofcombustion which may be formed with the fabric compositions describedabove. These improved fabric compositions are similar to those whichproduce products of combustion in all respects except that an inorganicbonding agent is substituted for the organic bonding agent of the priorart fabric compositions. When these fabric compositions with theinorganic bonding agent are exposed to high temperatures above about1750° F., no products of combustion in the form of smoke or fumes areproduced.

Another commonly assigned patent application, filed concurrentlyherewith, discloses the use of plasma spraying to form refractorycoatings on base fabric. These coated fabric compositions differ fromthose disclosed in the above patent and patent applications in thatplasma sprayed refractory coatings contain no added bonding agent.Further, the plasma spraying method permits the preparation of thinnerrefractory coatings than those of the prior art compositions.

The refractory coated fabric compositions disclosed in the commonlyassigned patent and patent applications may be usefully employed asinsulating tape for electrical conductors. Although these fabriccompositions exhibit good dielectric properties, the state of the artrequires flame resistant, electrical insulating compositions havingdielectric properties superior to those presently available.

It is an object of this invention to provide refractory coated fabriccompositions having improved dielectric properties.

It is another object of this invention to provide compositions which maybe usefully employed in insulating electrical conductors and which willexhibit superior dielectric properties as well as superior flame andheat resistance properties.

It is a further object of this invention to provide a dual functionfabric composition having superior dielectric and superior flame andheat resistance properties.

SUMMARY OF THE INVENTION

These and other objects of this invention have been achieved by forminga refractory coating on one side of a base fabric and adielectric-containing coating on the other side.

The present invention relates to a heat resistant, flexible refractoryinsulating composition comprising:

(a) a base fabric;

(b) a refractory coating comprising refractory materials, saidrefractory coating formed on one side of said fabric and said refractorymaterials being capable of fusing with the base fabric at elevatedtemperatures; and

(c) a dielectric coating comprising finely divided dielectric, saiddielectric coating formed on the other side of said fabric.

This invention also relates to the composition described hereinbeforeincluding the following additional element:

(d) a flock coating comprising flock fibers and an adhesive coating,said flock coating formed on said dielectric coating and said adhesivecoating securing said flock fibers to said dielectric coating with oneend of said fibers upstanding from said adhesive coating.

In another embodiment of this invention, the dielectric coatingadditionally comprises a resinous binder. Where a flock coating isapplied to this coating, an adhesive coating is not needed since theresinous binder may serve to secure the flock fibers to the dielectriccoating.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is an improvement over the heat resistant,flexible, refractory, insulating fabric compositions disclosed incommonly assigned U.S. Pat. No. 4,282,284, patent applications Ser. Nos.294,771, 294,770 and 225,888 and the commonly assigned concurrentlyfiled, patent application disclosing refractory coated fabriccompositions prepared by plasma spraying, the entire contents of saidpatent and patent applications being incorporated herein by reference.

Briefly, the fabric compositions of this invention have the samerefractory coating, formed on one side of the base fabric, as thatdisclosed in the above patent and patent applications. However, toimprove the dielectric properties of the composition, a coatingcontaining finely divided dielectric material is formed on the othersurface of the fabric. Further, a coating of flock fibers is optionallyformed on the dielectric coating. In addition, an abrasion resistantpolymer coating may be applied to the outer surface of the refractorycoating. Where the fabric composition is to be adhered to anothersurface or wrapped around an electrical wire or cable to provide aninsulated conductor, an adhesive may be appllied to the outer surface ofthe dielectric coating.

The compositions of this invention are utilized in those applicationswhich require an article which must exhibit specific multi-functionalproperties. Flame and heat resistance together with dielectricproperties are required where these compositions are employed aselectrical insulation in services where fire and heat damage wouldresult in loss of power and/or communication. Military installations,industrial plants and governmental crisis centers are examples oflocations where these compositions can be effectively used. Althoughideally a single material with the collective properties of theseinventive products would be preferred, finding and providing such amaterial at a reasonable price is usually a difficult task. In thepresent situation, a multi-layered product can provide the desiredproperties at a reasonable cost while meeting all essential productspecifications.

The base fabric employed in this invention may be composed of a materialwhich is flame resistant, such as fiberglass. One particularly usefulbase fabric is constructed of a knitted fiberglass where fiberglassyarns comprise both the knit and lay-in yarns of the base fabric.

Satisfactory results have been obtained employing knit yarns comprisedof DE type fiberglass with a yarn designation of DE-450-1/0 and fill orlay-in yarns comprised of fiberglass with a yarn designation ofDE-450-1/0.

As will be understood by those skilled in the art, the knit fiberglasssubstrate fabric, though preferably formed of all fiberglass yarns, maybe constructed with other kinds of fire resistant knit yarns or withonly the weft lay-in yarn comprised of fiberglass. The substrate or basefabric may also be a woven fiberglass or a non-woven fabric offiberglass.

As used herein the term "fabric" includes materials which are woven,knitted, non-woven or otherwise constructed from fibers. As explained inthe related commonly assigned patent and applications, there must be anopenness to the texture of the base fabric so as to permit therefractory coating to impregnate the surface of the fabric and fill, atleast partially, some, if not all, of the interstices of the porousfabric when the refractory coating is applied by roller or knife coatingtechniques. Thus knitted fabrics are preferred when this procedure isemployed. When the refractory coating is applied by plasma spraying inaccordance with the concurrently filed, commonly assigned patentapplication, either woven or knitted fabrics may be used.

In addition to fiberglass, aramid yarns of Kevlar fibers may be employedin the base fabric. Base fabrics containing yarns of fiberglass andKevlar fibers may also be employed. Further, base fabrics of quartzyarns or quartz yarns and Kevlar fiber yarns are useful. Similarly,non-woven webs or paper of ceramic fibers including alumina silicafibers, alumina fibers, zirconia fibers or mixtures thereof may serve asthe base fabric in this invention. Details on these fabrics arepresented in a concurrently filed and commonly assigned patentapplication directed to the plasma spraying preparation of fabriccompositions, the contents of said application are incorporated hereinby reference.

The dielectric coating which provides the superior dielectric propertiesexhibited by the compositions of this invention comprises finely divideddielectric material. The dielectric coating may be formed by plasmaspraying the finely divided dielectric material onto the base fabric orby admixing the dielectric material with a resinous binder which securesthe dielectric material to the base fabric.

Useful dielectric materials which may be employed in this inventioninclude mica, zirconium oxide and aluminum oxide. Additives whichimprove the properties of the zirconium oxide and aluminum oxide can beused if desired. These additives are metal titanates of such metals asbismuth, calcium, magnesium, strontium, lead, zinc-magnesium. Mixturesof such metal titanates may also be used.

The mica employed herein may be any of the natural micas which arecomposed of several silicates of varying chemical composition or asynthetic mica such as those which are electrochemically prepared.Synthetic mica is preferred since it has electrical and mechanicalproperties superior to those of the natural product and is also waterfree.

The dielectric materials should be finely divided, i.e., they should be325 mesh or smaller (<0.043 mm. particle diameter).

The dielectric coating may be formed by means of plasma spraying. Thisknown technique, as described hereinafter in connection with therefractory coating, does not require the use of a bonding agent. Inplasma spraying the finely divided dielectric materials become plasticor molten in the plasma and are the propelled onto the base fabric wherethey solidify forming a coating on the fabric surface.

Alternately, the dielectric can be admixed with any resin which willsecure it to the base fabric and which will remain flame resistant untilcarbonization occurs. Useful resins include epoxy resin, urethane resin,acrylic resin and the like. Particularly preferred resins are polyimideresin, polyamideimide resin and polyester resin. Useful polyimide resinand polyamideimide resin may be obtained from Rhone-Poulenc Chemical Co.of Monmouth Junction, N.J. under the tradenames Kerimid 500 andRhodeftal 200, respectively.

In general the weight of resin to dielectric must be sufficient for theresin to provide a sufficient degree of adhesiveness. Those skilled inthe art can determine the optimum ratio for the particular resin anddielectric employed without an undue amount of experimentation. With thepolyimide and polyamideimide resins not less than about 40 weightpercent resin will usually be found useful while with the other resins,such as polyester, not more than 30 weight percent resin will usually besufficient. These quantities can be adjusted higher or lower asrequired.

The dielectric coating may be applied to the base fabric before or afterthe refractory coating is applied. Those skilled in the art willappreciate that the particular order in which the several coatings andlayers are applied to the base fabric will be dependent on theparticular fabrication techniques employed, the number of coatings andlayers to be applied and the composition of the individual coatings andlayers.

Optionally, a flock coating of cotton, polyester, nylon, rayon ormixtures thereof may be applied to the outer surface of the dielectriccoating. The flock coating makes it easier to handle the finishedcomposition so that the surface roughness doesn't chaff or cut the handsof people using the composition. The flock coating consists of flockfibers upstanding from the dielectric coating. Where a resinous binderis employed as part of the dielectric coating, it can serve as aadhesive for securing one end of the flock to the dielectric coating.Where the dielectric coating is formed without a resinous binder, anadhesive coating may be applied to the surface of the dielectric coatingso as to secure one end of the flock fibers to the dielectric coating. Adescription of a method for the formation of the flock coating, as wellas useful adhesive coatings, is presented in U.S. Pat. Nos. 3,666,522and 3,968,284 of George, the contents of which are incorporated hereinby reference. In addition, other techniques such as air blowing may beused.

The refractory coating which is applied to the other side of the basefabric may consist of fused refractory materials formed thereon byplasma spraying as disclosed in one of the commonly assigned patentapplications filed concurrently herewith or refractory materials plus anorganic or an inorganic bonding agent as disclosed in the abovedescribed commonly assigned patent and patent applications, filedheretofore. The entire contents of U.S. Pat. No. 4,282,284, theconcurrently filed patent application and patent application Ser. Nos.294,770 and 294,771 are incorporated herein by reference.

The refractory coating which is applied to the surface of the basefabric comprises heat resistant refractory materials which may be any ofthe usual known refractory materials in finely divided form which willfuse with the base fabric when subjected to elevated temperatures, e.g.,above about 1250° F., for fiberglass, and includes compounds ofaluminum, calcium, chromium, magnesium, silicon, titanium, zirconium andthe like, such as aluminum oxide, calcium oxide, magnesium oxide,silicon oxide, titanium oxide, zirconium oxide, aluminum silicate,calcium silicate, magnesium silicate, silicon carbide, zirconiumcarbide, alumina silica fiber and the like. Alumina, zirconia, calciumsilicate and silicon dioxide are preferred, alone or in combination.These materials enable the compositions of this invention to maintaintheir heat insulating ability during prolonged exposure (about 20minutes) to temperatures in the 1800°-2000° F. range.

In addition to these ceramic-type materials, other useful refractorymaterials may be employed to provide compositions which will withstandthermal shock at temperatures in the 4000° F. plus range. Theserefractory materials include, for example, zirconium oxide, siliconcarbide, and thermal carbon black. This latter material is anon-electrical conducting form of carbon black which is resistant tothermal shock temperatures as high as 7000° F.

Plasma spraying is a well known process for forming metallic, refractoryor ceramic coatings on substrates. When employed to provide refractorycoatings on a non-rigid base fabric, this technique, as disclosed in theconcurrently filed patent application, does not require the use of abonding agent to form the refractory coating. The high temperatureplasma causes the powdered refractory materials to become plastic ormolten. This refractory material is then propelled to the base fabricwhere it solidifies, forming a coating on the surface of the fabric. Thethickness of the film as well as the density of the coating can beclosely controlled in this process. In fact, refractory films as thin as1-1.5 mils may be laid down to provide a thin, lightweight product whichis particularly useful in the aerospace and allied industries whereweight and space are often of critical importance.

Alternatively, an organic or an inorganic bonding agent may be admixedwith the refractory material and applied to the porous base fabric toprovide a refractory coating. Useful organic bonding agents includeacrylic latex resin alone or in combination with colloidal silica asdisclosed in U.S. Pat. No. 4,284,284. Another bonding agent, disclosedin U.S. patent application Ser. No. 294,770, contains polyurethane resinand monoaluminum phosphate.

An inorganic composition, employed as the bonding agent, is disclosed inU.S. patent application Ser. No. 294,771 and comprises colloidal silica,monoaluminum phosphate and aluminum chlorohydrate. This inorganiccomposition is combined with the refractory materials to form therefractory coating. This coating is applied to the porous base fabricand then subjected to drying to cause the removal of water and a bondingof the refractory material to the porous base fabric. A saturationcoating of the inorganic composition is then applied over the refractorybase coating and dried. This saturation coating provides additionalchemical bonding between the porous base fabric and the refractorymaterials creating a more secure bond of these refractory materials tothe porous base fabric. Further, the saturation coating of the inorganiccomposition, when fully dried, provides a smooth surface to the fabriccomposition.

This inorganic composition is liquid and is formed from colloidalsilica, monoaluminum phosphate and aluminum chlorohydrate. The lattertwo materials cannot normally be employed in combination since when theyare combined the result is highly exothermic, producing a solid materialwhich becomes adhesive. By employing the colloidal silica, which acts asa liquid moderator, the monoaluminum phosphate (MAP) and the aluminumchlorohydrate (ACH) may be used in combination to achieve the desiredresults. Further details regarding this inorganic bonding agent arepresented in application Ser. No. 294,771.

One particularly preferred group of bonding agents for the refractorycoating is the polyimide, the polyamideimide and the polyester resinsdisclosed herein as those which can usefully be employed in thedielectric coating.

A particularly useful refractory coating has the following formulation:

    ______________________________________                                        Component              Parts by weight                                        ______________________________________                                        Polyester Resin                                                               Vital 200 solution     26                                                     20% solids in Toluene                                                         Mfg. by: Goodyear Tire & Rubber Co.                                           Akron, Ohio                                                                   Aluminum Hydrate                                                              SB 632                 18                                                     Mfg. by: Solem Industries                                                     Atlanta, Georgia                                                              Alumina Silica Fiber                                                          Fiberfrax (ball milled)                                                                              20                                                     Mfg. by: The Carborundum Co.                                                  Niagara Falls, New York                                                       Total parts            64                                                     ______________________________________                                    

A refractory coating, particularly useful with fiberglass fabrics foruse at high temperatures, has the following formulation:

    ______________________________________                                        Component              Parts by Weight                                        ______________________________________                                        Polyamideimide Resin                                                          Rhodeftal 200          40                                                     Mfg. by: Rhone-Poulenc Chemical Co.                                           Monmouth Junction, N.J.                                                       Alumina Silica Fiber                                                          Fiberfrax (ball milled)                                                                              20                                                     Mfg. by: The carborundum Co.                                                  Niagara Falls, N.Y.                                                           Zirconium Oxide                                                               Tam Zirox 250          12                                                     Mfg. by: Tam Ceramics Inc.                                                    Niagara Falls, N.Y.                                                           Aluminum Hydrate                                                              SB 632                 10                                                     Mfg. by: Solem Industries                                                     Atlanta, Georgia                                                              Silicone Fluid                                                                Rhodorsil 48V750       1                                                      Mfg. by: Rhodia Inc.                                                          Monmouth Junction, N.J.                                                       Total parts            83                                                     ______________________________________                                    

When this formulation is applied to fiberglass fabric, the resin itselfwill provide thermal protection up to about 1200° F. for short periods.By applying this refractory coating to fiberglass fabrics containingyarns of different sizes, for example, DE-450-1/0 and DE-150-1/0 yarns,the resultant fabric compositions provide thermal resistance in astep-wise fashion. From room temperature to about 500°-600° F., theresin provides essentially all the thermal protection for thefiberglass. Beyond about 500°-600° F., the fiberglass yarns soften andthen fuse with the remaining components of the refractory coating--thethinner yarns softening at the lower temperatures, about 600° to about900° F., with the heavier yarns softening at above 900° F. Theseparticular fabric compositions will withstand impact or thermal shocktemperatures of 1800°-2000° F.

Where the fabric composition will be subject to abrasive forces atambient temperatures, a polymeric coating as described in the abovecommonly assigned patent and patent applications, may be applied overthe saturation coating. In preferred embodiments, polyimide resin,polyamideimide resin or polyester resin is employed as the polymercoating instead of the polyvinylchloride disclosed in said patent andpatent applications. This polymeric coating may be applied at a coatingdensity of approximately 2 ounces per square yard, based on dry netweight, to improve the surface abrasion qualities of the fabric and toseal in and contain any refractory materials that may otherwise loosenfrom the fabric as it is stretched in the wire and/or cable wrappingprocess or subject to abrasion in use.

The polymer used in the polymeric coating should remain flame resistantuntil carbonization occurs. Polyvinyl chloride resin is one polymerwhich may be used in the polymeric coating. This coating is a mixture ofselected plasticizers, stabilizers and modifiers, dispersion resins andoxides. A number of components are combined with the polyvinyl resin toprovide the required properties of high temperature resistance andflexibility. One such polyvinyl chloride resin formulation is describedin the above commonly assigned patent and patent applications which havebeen incorporated herein by reference. However, it is preferred that thepolyimide resin, the polyamideimide or the polyester resin disclosedherein as being useful in the dielectric coating and the refractorycoating be employed as the abrasion resistant polymeric coating.

Where an adhesive is to be applied to the dielectric coating to adherethe fabric composition to, for example, an electrical wire or a surfacerequiring heat and flame protection, the flameproof tape wrappingadhesive disclosed in U.S. Pat. No. 4,282,284 may be employed.

The fabrics prepared in accordance with this invention may be employedin the same manner as those disclosed in the commonly assigned patentand patent applications referred to hereinabove. Thus, they may serve,for example, as electrical insulating tape, welding curtains and mats,pipe and dust insulation, fire resistant linings and the like where amaterial is required which is capable of enduring high temperatures andproviding thermal protection and dielectric properties.

What is claimed is:
 1. A heat resistant, flexible refractory insulatingcomposition comprising:(a) a base fabric, (b) a refractory coatingcomprising refractory materials, said refractory coating formed on oneside of said fabric and said refractory materials being capable offusing with the base fabric at elevated temperatures; and (c) adielectric coating comprising a finely divided dielectric which is mica,zirconium oxide or aluminum oxide, the zirconium oxide and aluminumoxide additionally containing a titanate of bismuth, calcium, magnesium,strontium, lead, zinc-magnesium or mixtures thereof, said dielectriccoating formed on the other side of said fabric.
 2. A compositionaccording to claim 1 wherein said dielectric coating is formed on saidbase fabric by plasma spraying.
 3. A composition according to claim 1wherein said dielectric coating additionally comprises a resinousbinder.
 4. A composition according to claim 2 including the followingadditional element:(d) a flock coating comprising flock fibers and anadhesive coating, said flock coating formed on said dielectric coatingand said adhesive coating securing said flock fibers to said dielectriccoating with one end of said fibers upstanding from said adhesivecoating.
 5. A composition according to claim 3 including the followingadditional element:(e) a flock coating comprising flock fibers, saidflock coating formed on said dielectric coating and said resinous bindersecuring said flock fibers to said dielectric coating with one end ofsaid fibers upstanding from said resinous binder.
 6. A compositionaccording to claims 3 or 5 wherein the resinous binder is epoxy resin,urethane resin or acrylic resin.
 7. A composition according to claims 3or 5 wherein the resinous binder is polyimide resin, polyamideimideresin or polyester resin.
 8. A composition according to claims 4 or 5wherein the flock fibers are cotton, polyester, nylon, rayon or mixturesthereof.
 9. A composition according to claim 1 wherein said refractorycoating is formed on said base fabric by plasma spraying.
 10. Acomposition according to claim 1 wherein said refractory coatingadditionally comprises a bonding agent and said composition includes thefollowing additional element:(f) a saturation coating formed on theoutside surface of said refractory coating, said bonding agent and saidsaturation coating being an inorganic composition comprising colloidalsilica, monoaluminum phosphate and aluminum chlorohydrate.
 11. Acomposition according to claim 1 wherein said refractory coatingadditionally comprises a bonding agent, said bonding agent being acryliclatex resin or acrylic latex resin and colloidal silica.
 12. Acomposition according to claims 1 or 5 including the followingadditional element:(g) an abrasion resistant polymeric coating formed onthe outside surface of said refractory coating.
 13. A compositionaccording to claims 1, 4 or 5 including the following additionalelement:(h) an adhesive applied to the outside surface of saiddielectric coating.
 14. A composition according to claim 12 wherein saidrefractory coating additionally comprises a bonding agent, said bondingagent and said polymeric coating being polyimide resin, polyamideimideresin or polyester resin.
 15. A composition according to claim 1 whereinthe base fabric is a knitted fabric.
 16. A composition according toclaim 1 wherein the fabric is a woven fabric or a non-woven fabric. 17.A composition according to claims 15 or 16 wherein the base fabric ismade from fiberglass yarn, Kevlar yarn or a mixture of fiberglass yarnand Kevlar yarn.
 18. A composition according to claim 1 wherein therefractory materials are alumina, zirconia, calcium silicate, silicondioxide or mixtures thereof.
 19. A composition according to claim 1wherein the refractory materials are silicon carbide or thermal carbonblack.
 20. A composition according to claim 1 wherein said base fabricis made from fiberglass yarn and said refractory coating comprisespolyamideimide resin, alumina silica fiber, zirconium oxide and aluminumhydrate.
 21. A composition according to claims 15 or 16 wherein the basefabric is made from quartz yarn or a mixture of quartz yarn and Kevlaryarn.
 22. A composition according to claim 1 wherein the base fabric isa non-woven web or paper of alumina silica fibers, alumina fibers,zirconia fibers or mixtures thereof.